1. Field of the Invention
The present invention relates to an apparatus and a method for performing a developing procedure by supplying a developer solution to a surface of a substrate with photoresist being applied thereto and exposed to light.
2. Description of the Background Art
In a photolithography step which is one of the steps of manufacturing semiconductors, photoresist is applied onto a thin film formed on a surface of a semiconductor wafer (hereinafter wafer W) for example, the photoresist is exposed to light with a predetermined pattern, and then a mask pattern is formed through development. This photolithography procedure is generally performed by means of a system including an application/development unit for resist application and development and an exposure unit coupled to the application/development unit.
Referring to FIG. 14, according to a method of developing a wafer W which has been exposed, a nozzle 1 is used that has a discharge opening formed over a distance corresponding to the diameter of wafer W, and this nozzle 1 held above wafer W at a distance of approximately 1 mm is moved, with respect to a surface of wafer W held horizontally on a spin chuck 11, from the rear end of wafer W toward the front end thereof, so that a developer solution 12 supplied from the discharge opening of nozzle 1 is spread over the surface of wafer W to form a liquid film of approximately 1 mm in thickness over the entire surface of wafer W.
The above-discussed method has to address the following problem. This problem arises from the fact that, after nozzle 1 moving toward the front end of wafer passes over the diameter part (the center) of circular wafer W while supplying developer solution 12, the length of the effective region of wafer W relative to the length of nozzle 1 decreases gradually. In this case, as viewed from a certain part of the perimeter of wafer W, nozzle 1 moves away from this certain part while discharging developer solution 12, and this discharged developer solution does not fall immediately below the discharge opening but drawn by and coupled to the liquid film (developer solution) which has already been spread on the surface of wafer W due to the surface tension. This is because of the low discharge pressure of nozzle 1, the discharge pressure corresponding approximately to the own weight of developer solution 12. As nozzle 1 moves further toward the front end of wafer W, the surface tension cannot keep drawing developer solution 12 being supplied from the discharge opening, and consequently, the developer solution is severed between a part of the developer solution having been applied to the surface of wafer W and another part of the developer solution not to be applied to the surface of wafer W. In other words, nozzle 1 moves while discharging the developer solution which is separated between a part of the discharge opening of nozzle 1 that does not face the surface of wafer W and the certain peripheral part of wafer W away from the part of the discharge opening. In the severed developer solution, a returning force is generated that causes the severed developer solution to be returned (drawn) to developer solution 12 already spread on the surface of wafer W. This returning force causes a flow of developer solution 12 from the peripheral region of wafer W toward the center thereof, for example. The returning force is particularly great at the front end of wafer W, the returning force generated when nozzle 1 is moving away from the surface of wafer W. At this time, the returning force could cause waves in the developer solution 12 spread over the surface of wafer W. As a result, the uniformity of the line width accuracy of a mask pattern obtained after the development deteriorates, which has been found by the inventors of the present invention.
Referring to FIG. 15, according to a method devised for solving the above-discussed problem, a knife ring 13 is provided on the perimeter of wafer W to suitably sever the developer solution at the perimeter of wafer W. However, because of the low discharge pressure of developer solution 12 supplied from nozzle 1 that corresponds approximately to the own weight of the developer, the surface tension of the developer solution could work on the solution-severing face of knife ring 13 to hinder the developer solution from being appropriately severed.
The present invention has been made in consideration of the above-described circumstances. One object of the present invention is to provide a technique, in a development process for a substrate having undergone exposure, of allowing a developer solution to be applied onto a surface of the substrate without causing flow and waves in the developer solution spread over the surface of the substrate, thereby producing a mask pattern with a highly uniform line width.
According to the present invention, a developing apparatus is used for developing a substrate, with photoresist applied onto a surface of the substrate and exposed. The developing apparatus includes a substrate-holding unit holding the substrate in a horizontal state, a supply nozzle supplying a developer solution to the substrate, the supply nozzle having a discharge opening formed over a distance almost equal to or longer than the width of an effective region of the substrate, a moving mechanism moving the supply nozzle from a rear end of the substrate toward a front end of the substrate, and a solution-receiving plate having solution-passing holes for passing the developer solution therethrough toward the back of the solution-receiving plate, the solution-receiving plate being provided at least on the front-end side of the substrate and separated by a slight distance from the front end of the substrate, and the solution-receiving plate and the surface of the substrate being at the same height or the solution-receiving plate being at a height slightly lower than that of the surface of the substrate. The substrate is a semiconductor wafer for example and the solution-receiving plate is provided along a front half of the perimeter of the semiconductor wafer, the front half of the perimeter extending from one end of a diameter of the wafer that is in parallel with the supply nozzle to the other end of the diameter through the front end of the wafer. The developing apparatus further includes a cup surrounding, for example, the substrate held on the substrate-holding unit and freely moving up/down, and the solution-receiving plate is provided on an upper end of the cup. The substrate is separated from the solution-receiving plate by a distance of 0.5 mm to 3 mm. The solution-receiving plate is placed at a height lower than that of the surface of the substrate by 0.3 mm to 2.5 mm. The solution-receiving plate may be inclined downward with respect to the perimeter of the substrate.
Further, according to the present invention, a developing apparatus is used for developing a substrate, with photoresist applied onto a surface of the substrate and exposed. The developing apparatus includes a substrate-holding unit holding the substrate in a horizontal state, a supply nozzle supplying a developer solution to the substrate, the supply nozzle having a discharge opening formed over a distance almost equal to or longer than the width of an effective region of the substrate, and a moving mechanism moving the supply nozzle from a rear end of the substrate toward a front end of the substrate. The discharge opening is curved toward the front end of the substrate so that two lateral ends of the discharge opening are located back with respect to the center of the discharge opening.
Moreover, a developing apparatus is used for developing a substrate, with photoresist applied onto a surface of the substrate and exposed. The developing apparatus includes a substrate-holding unit holding the substrate in a horizontal state, a supply nozzle supplying a developer solution to the substrate, the supply nozzle having a discharge opening formed over a distance almost equal to or longer than the width of an effective region of the substrate, a moving mechanism moving the supply nozzle from a rear end of the substrate toward a front end of the substrate, and airflow generating means for generating an airflow over the surface of the substrate to prevent a flow from being produced in the developer solution on the substrate. The airflow generating means has air-discharge holes arranged along the perimeter of the substrate, and the airflow generating means is provided to freely move up/down.
When the developer solution is discharged from the supply nozzle to be applied onto the surface of the substrate, a part of the developer solution extended continuously from the supply nozzle to the perimeter of the substrate by the action of the surface tension is severed and then the severed developer solution returns to the developer solution already spread over the substrate. According to the present invention, the developer solution is applied to the surface of the substrate without causing the returning of the developer solution. Then, no flow and wave occur in the developer solution spread over the surface of the substrate and accordingly a mask pattern of a highly uniform line width is obtained.
According to the present invention, a developing method is used for developing a substrate, with photoresist applied onto a surface of the substrate and exposed. The developing method includes the steps of holding the substrate in a horizontal state on a substrate-holding unit, placing, a solution-receiving plate having solution-passing holes, at least on a front-end side of the substrate with respect to the direction in which a supply nozzle is moved, the solution-receiving plate being separated by a slight distance from the front end of the substrate, and the solution-receiving plate and the surface of the substrate being at the same height or the solution-receiving plate being at a height slightly lower than that of the surface of the substrate, and thereafter moving the supply nozzle for supplying a developer solution to the substrate, the supply nozzle having a discharge opening formed over a distance almost equal to or longer than the width of an effective region of the substrate, the supply nozzle being moved from a rear end of the substrate toward the front end of the substrate to apply the developer solution to the surface of the substrate while a part of the developer solution discharged from a part of the discharge opening located outside the substrate is passed through the solution-passing holes of the solution-receiving plate toward the back of the solution-receiving plate. The solution-receiving plate is provided on an upper end of a cup surrounding the substrate held on the substrate-holding unit and freely moving up/down. The substrate is separated from the solution-receiving plate by a distance of 0.5 mm to 3 mm. The solution-receiving plate is placed at a height lower than that of the surface of the substrate by 0.3 mm to 2.5 mm. The solution-receiving plate may be inclined downward with respect to the perimeter of the substrate.